How to use: Connected to 5V power supply, the power indicator light, sensor board is not water droplets, DO output is high, the switch lights off, dropping on a drop of water, DO output is low, the indicator light switch, Brush off the the above water droplets, has returned to output high state. . . . AO analog output can be connected to the microcontroller AD port to detect the size of the drops in the above rainfall. DO TTL digital outputs can also be connected to the microcontroller detects whether there is rain.